Using an ab initio TD-DFT approach systematically accounting for the molecular surrounding effects, we have computed the n --> pi* absorption wavelength of azobenzenes. A large set of functionals has been reviewed for the determination of transition energies and structural parameters. The blend of a range-separated hybrid for modelling the excited-states and a global hybrid (PBE0) for the ground-state description finally gave the most accurate results both in terms of absolute wavelength, and chemical ranking. On the contrary, complete range-separated calculations, or use of the M05 functional, were less satisfying. (C) 2008 Elsevier B.V. All rights reserved.